1. Field of the Invention
The present invention relates to a three-dimensional image-capturing device that detects the three-dimensional shape of a measurement subject by means of a time-of-flight measurement.
2. Description of the Related Art
An example of an active-system three-dimensional image-capturing device, which detects the three-dimensional shape of a subject, is disclosed in “Measurement Science and Technology” (S. Christies et al., vol. 6, p.1301–1308, 1995) and in International Publication No. WO 97/01111. In “Measurement Science and Technology”, a pulse modulated laser beam is divergently emitted to a measurement subject from a device and the reflected light from the subject is received by a two-dimensional CCD sensor to which an image-intensifier is attached, so that received light energy is converted to electric signals. The shutter operation is carried out with the image-intensifier which is controlled by a gate-pulse, and the gate-pulse is synchronized with the pulse radiation of the laser beam. According to the above construction of the device, the amount of light received during the exposure time at each pixel of the CCD correlates with the distance between the pixel and the corresponding point on the subject, so that electric signals which correspond to the distance of the subject are obtained for each pixel of the CCD.
In International Publication No. 97/01111, a device divergently emits pulse modulated light, such as a laser beam, to a measurement subject and the reflected light is received at the two-dimensional CCD sensor which is assembled with a mechanical shutter or an electro-optical shutter formed by a liquid crystal display, so that received light energy is converted to electric signals. The shutter is controlled at a timing which is different from that of the laser emission. Distance information of the measurement subject is obtained at each pixel of the CCD.